Integrated cardiac mapping and ablation probe

ABSTRACT

A probe for cardiac diagnosis and/or treatment has a catheter tube. The distal end of the catheter tube carries first and second electrode elements. The probe includes a mechanism for steering the first electrode element relative to the second electrode element so that the user can move the first electrode element into and out of contact with endocardial tissue without disturbing the contact of the second electrode element with endocardial tissue, even through the two electrode elements are carried on a common catheter tube. The distal end can carry a three dimensional structure having an open interior area. One of electrode elements can be steered through the open interior area of the structure. Electrode elements on the exterior of the structure can be used for surface mapping, while the electrode element inside the structure is steered to ablate tissue.

This a continuation of application Ser. No. 08/583,939, filed on Jan. 4,1996, now U.S. Pat. No. 5,881,727, which is a continuation ofapplication Ser. No. 08/136,648, filed on Oct. 14, 1993, now abandoned.

FIELD OF THE INVENTION

The invention relates to systems and methods for mapping and ablatingthe interior regions of the heart for treatment of cardiac conditions.

BACKGROUND OF THE INVENTION

Physicians make use of catheters today in medical procedures to gainaccess into interior regions of the body to ablate targeted tissueareas. It is important for the physician to be able to carefully andprecisely control the position of the catheter and its emission ofenergy within the body during tissue ablation procedures.

The need for careful and precise control over the catheter is especiallycritical during procedures that ablate tissue within the heart. Theseprocedures, called electrophysiological therapy, are becoming morewidespread for treating cardiac rhythm disturbances.

During these procedures, a physician steers a catheter through a mainvein or artery into the interior region of the heart that is to betreated. The physician then further manipulates a steering mechanism toplace the electrode carried on the distal tip of the catheter intodirect contact with the tissue that is to be ablated. The physiciandirects energy from the electrode through tissue to an indifferentelectrode (in a uni-polar electrode arrangement) or to an adjacentelectrode (in a bi-polar electrode arrangement) to ablate the tissue andform a lesion.

Cardiac mapping can be used before ablation to locate aberrantconductive pathways within the heart. The aberrant conductive pathwaysconstitute peculiar and life threatening patterns, called dysrhythmias.Mapping identifies regions along these pathways, called foci, which arethen ablated to treat the dysrhythmia.

There is a need for cardiac mapping and ablation systems and proceduresthat can be easily deployed with a minimum of manipulation and effort.

There is also a need for systems and procedures that are capable ofperforming cardiac mapping in tandem with cardiac ablation. Suchmultipurpose systems must also be easily introduced into the heart. Oncedeployed, such multipurpose systems also must be capable of mapping andablating with a minimum of manipulation and effort.

SUMMARY OF THE INVENTION

A principal objective of the invention is to provide improved probes tocarry out cardiac mapping and/or cardiac ablation procedures quickly andaccurately.

Another principal objective of the invention is to provide improvedprobes that integrate mapping and ablation functions.

One aspect of the invention provides a probe having a catheter body. Thedistal end of the catheter body carries first and second operativeelements. In use, the operative elements make contact with endocardialtissue independently of each other to perform therapeutic or diagnosticfunctions. According to this aspect of the invention, the probe includesa mechanism for steering the first operative element without alteringthe position of the second operative element.

According to this aspect of the invention, the user can move the firstelectrode element into and out of contact with endocardial tissuewithout disturbing the contact of the second electrode element withendocardial tissue, even though the two electrode elements are carriedon a common catheter body. This aspect of the invention permits thefirst and second operative elements to perform the same or differentfunctions.

For example, in a preferred embodiment, the first operative elementserves to ablate myocardial tissue. The second operative elementindependently serves to sense electrical activity in endocardial tissue.

In this arrangement, the second operative element comprises one or moreelectrodes that map endocardial tissue to locate foci to be ablated. Thefirst operative element can be steered to the foci located by themapping electrodes, without interfering with their mapping function.

In one preferred embodiment, the second operative element can beoperated to ablate myocardial tissue by thermal or chemical means,independently of the mapping function performed by the first electrodeelement.

In another aspect of the invention, the distal end of the catheter bodycarries a three dimensional structure having an open interior area. Thestructure has an exterior surface for contacting endocardial tissue.According to this aspect of the invention, the probe includes anoperative element that extends from the distal end of the catheter bodyinto the open interior area of the structure. The probe includes amechanism for steering the operative element through the open interiorarea.

This aspect of the invention provides a three dimensional structure thatsurrounds the operative element to stabilize its position during use.The user can steer the operative element through the stabilizingstructure to make selected contact with endocardial tissue.

In a preferred embodiment, the operative element ablates myocardialtissue. In this arrangement, the ablating element can take the form ofan electrode that thermally destroys myocardial tissue. Alternatively,the ablating element can inject a chemical substance that destroysmyocardial tissue.

In a preferred embodiment, the exterior surface of the structure carrieselectrode elements for sensing electrical activity in endocardialtissue. In this arrangement, the exterior electrode elements can be usedto map the surface of endocardial tissue, while the interior element canbe independently steered into position to ablate the tissue. This aspectof the invention provides a probe that integrates mapping and ablationfunctions.

Other features and advantages of the inventions are set forth in thefollowing Description and Drawings, as well as in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a probe and monitoring system thatembodies the features of the invention;

FIG. 2 is a plan view of the interior of the handle for the steerablecatheter, partially broken away and in section, showing the mechanismfor steering the distal tip of the catheter body;

FIG. 3 is a plan view showing the exterior of the handle of FIG. 2;

FIG. 4 is a fragmentary side cross sectional view of the handle of takenalong Line 4--4 of FIG. 3;

FIG. 5 is a fragmentary sectional view on a greatly enlarged scaleshowing the mapping electrode deployment mechanism;

FIG. 6 is a plan view of an electrode-carrying basket and movable guidesheath shown in FIG. 1, with portions fragmented and in section, showingthe electrode-carrying basket in a retracted condition;

FIG. 7 is a plan view of the handle showing the mapping basket controlin the deployed position;

FIG. 8 is a view, partially broken away and in section, showing theguide sheath and the steerable catheter body advanced into thedeployment position;

FIG. 9 is a plan view of the handle showing the mapping basket controlin the deployed position illustrating use of the steering controlmechanism to steer the ablation catheter;

FIG. 10 is a view, partially broken away and in section, showing theguide sheath and the steerable catheter body advanced into thedeployment position with the ablation electrode steered into positionfor use;

FIG. 11 is a plan view of the handle illustrating steering of the probewith the electrode-carrying basket retracted; and,

FIG. 12 is an enlarged plan view of probe distal tip illustratingsteering of the probe with the electrode-carrying basket retracted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an endocardial mapping system 10 that embodies features ofthe invention.

The system 10 includes a catheter probe 12.

The catheter probe 12 includes a handle 14, to which a flexible guidebody 16 is attached.

The distal end of the guide body 16 carries a three dimensionalstructure 18. The structure 18 takes the form of a basket, as best shownin FIGS. 8 and 10.

The three dimensional basket structure 18 includes an exterior surface28 that encloses an open interior area 30. The basket structure 18carries a three dimensional array of electrodes 32 on its exteriorsurface 28. When deployed inside the heart chamber, the exterior surface28 of the basket structure 18 holds the electrodes 32 against theendocardial surface.

According to the invention, the three dimensional structure 18 carrieswithin it a steerable ablating element 20. The ablating element 20 ismoveable through the interior area 20 without requiring movement of thestructure 18 itself.

As FIG. 5 best shows, the guide body 16 comprises a multi-layer tubularconstruction. It includes at its core a length of stainless steel coiledinto a flexible spring 22 enclosing an interior bore 24. A braidedsheath 26 of plastic material surrounds the guide spring 22.

As FIG. 5 also shows, the guide body 16 also includes an outer sheath 34that surrounds the inner sheath 26. The outer sheath 34 is made from aninert plastic material, which, in the preferred embodiment, comprises anylon composite material. The sheath 34 has an inner diameter that isgreater than the outer diameter of the inner sheath 26. As a result, theouter sheath 34 can slide along the inner sheath 26.

The handle 14 carries a control knob 36, which is attached to the sheath16 (see FIGS. 2 to 4). Forward movement of a control knob 36 (see FIG.11) advances the distal end of the slidable sheath 34 upon the basketstructure 18. The slidable sheath 34 captures and collapses the basketstructure 18 (as FIGS. 6 and 12 show). In this position, the distal endof the sheath 34 entirely encloses the basket structure 18. Thephysician introduces the basket structure 18 into the selected heartchamber through a selected vein or artery when in this collapsed, lowprofile condition.

Rearward movement of the control knob 36 (see FIGS. 7 and 8) retractsthe slidable sheath 34 away from the basket structure 18. The basketstructure 18 opens to assume its prescribed three dimensional shape, asFIG. 8 shows. The basket structure 18 is thereby deployed for use withinthe heart chamber.

The basket 18 can be variously constructed. In the illustrated andpreferred embodiment (best shown by FIGS. 9 and 11), the basket 24comprises an annular base member 38 attached about the inner sheath 26.The basket 24 also includes an end cap 34.

Generally flexible splines 42 extend in a circumferentially spacedrelationship between the base member 38 and the end cap 40. In theillustrated embodiment, six splines 42 form the basket 18. However,additional or fewer splines 42 could be used, depending upon theapplication.

In this arrangement, the splines 42 are made of a resilient inertmaterial, like Nitinol metal or silicone rubber. The splines 42 areconnected between the base member 38 and the end cap 40 in a resilient,pretensed condition, as shown in FIG. 10. In this configuration, theresilient splines 42 bend and conform to the tissue surface theycontact.

As FIGS. 6 and 12 show, the splines 42 also collapse into a closed,compact bundle in response to an external compression force, which theexternal sheath 34 provides.

In the illustrated embodiment (as FIG. 8 shows), each spline 42 carriessix electrodes 32. Of course, additional or fewer electrodes 32 can beused. In the preferred embodiment, the electrodes 32 are made ofplatinum or gold plated stainless steel.

Signal wires 44 made from a highly conductive metal, like copper, leadfrom the electrodes 32. The signal wires 44 extend down the associatedspline 42, through the base member 38, and into the bore 24 of the guidespring 22 (see FIGS. 5 and 6). An inert plastic electrically insulatingsheath preferably covers each spline 42 to also enclose the signal wires44. In the preferred embodiment, the sheath is made of a polyurethaneelastomer.

The six signal wires 44 for each spline 42 are twisted together to forma common bundle 46 (see FIGS. 5 and 6). As FIGS. 5 and 6 show, thecommon bundle 46 is, in turn, passed through the bore 24 of the guidespring 22 and into the probe handle 14 (see FIG. 2).

The thirty six signal wires 44 attach via a signal cable to an externalcontroller 50, as FIG. 1 shows.

When deployed, the electrodes 32 record the electrical potentials inmyocardial tissue. The controller 50 derives the activation times, thedistribution, and the waveforms of the potentials recorded by the basketelectrodes 32. As FIG. 1 shows, displays 52 can be provided to indicateelectrical potential measurements at each electrode 32.

In an alternative arrangement, ablating energy can be applied through aselected one or more of the basket electrodes 32.

In the illustrated and preferred embodiment, the movable ablatingelement 20 is an integral part of the probe 18. The type of ablatingenergy used can vary. The physician can ablate tissue by using anelectrode to thermally destroy myocardial tissue, either by heating orcooling the tissue. Alternatively, the physician can inject a chemicalsubstance that destroys myocardial tissue. The physician can use othermeans for destroying myocardial tissue as well.

In the illustrated embodiment, the ablating element 20 takes the form acoaxial antenna assembly that emits electromagnetic microwave energy.The ablating antenna assembly 20 extends beyond the distal end of theguide spring 22 and its associated inner sheath 26.

The details of the microwave antenna assembly 20 and its attachment tothe guide spring 22 are shown in copending application Ser. No.07/868,031, filed Apr. 13, 1992, entitled "Steerable Antenna Systems forCardiac Ablation that Minimize Tissue Damage and Blood Coagulation Dueto Conductive Heating Patterns," which is incorporated herein byreference.

The ablating antenna assembly 20 includes an antenna 54 (see FIG. 6).The antenna 54 forms a helix with about 10 turns. Based upon its sizeand helical pattern, the operating frequencies of the antenna 54 iseither about 915 MHz or 2450 Mhz.

The antenna assembly 20 includes an associated coaxial cable 56. Thecable 56 extends from within the handle 14 (see FIG. 2) along theoutside of the guide spring 22 and within the sheath 32 (see FIG. 5). Asupply cable 58 (see FIGS. 1 and 2) is joined to the proximal end of theantenna cable 56. The supply cable 58 conducts microwave ablating energyfrom the controller 50 to the antenna 54 for propagation at the lesionsite.

The ablating antenna assembly 20 includes its own steering assembly 74.The steering mechanism 74 for the ablating antenna assembly 20 may vary.In the illustrated embodiment, the steering mechanism 74 is of the typeshown in copending application Ser. No. 07/868,031, which is identifiedabove and which is also incorporated herein by reference.

In the illustrated embodiment (see FIG. 2), the steering mechanism 74includes an interior cam wheel 76 located within the handle 14. Anexternal steering lever 78 (see FIG. 3) rotates the cam wheel 76. Thecam wheel 76 holds the proximal ends of right and left steering wires80.

As FIG. 2 shows, steering wires 80 extend from the associated left andright side surfaces of the cam wheel 76. The steering wires 80 extendthrough the bore 24 guide spring 22 (see FIG. 5) to the ablating antennaassembly 20.

The steering wires 80 attach to opposite sides to a steering spring 60(see FIG. 6). The steering spring 60 is, in turn, soldered to the distalend of the antenna cable 56.

The helix antenna 54 extends distally from this juncture, being enclosedwithin a shroud 62 of potting compound. The potting compound shroud 62preferable includes a particles of diamond or sapphire that provide ahigh dielectric constant; low microwave energy loss; and high thermalconductivity.

When the ablation element 20 is deployed out of the sheath 34 (as FIGS.9 and 10 show), forward movement of the steering lever 78 bends theablation element 20 down (as shown in phantom lines) while rearwardmovement bends the ablation element 20 up (as shown in solid lines). Theelement 20 moves through the basket 18 between a generally straightconfiguration (as FIG. 8 shows) and the up and down deflected positions(as FIGS. 9 and 10 show), to selectively place the ablating element 20in contact with endocardial tissue.

By manipulating the steering lever 78, the physician can maneuver theablating element 20 under fluoroscopic control through the basket 18into contact with any point of the endocardial surface of the chamber.The ablating element 20 can be moved through the basket 18 to tissuelocations either in contact with the exterior surface of the basket 18or laying outside the reach of the basket 18 itself. Ablating energy canthen be applied to thermally destroy the tissue.

Furthermore, as FIGS. 11 and 12 show, by manipulating the steering lever78 when the outer sheath 34 is moved forward, the physician can maneuveror steer the entire distal tip of the probe 18 during its introductioninto the selected heart chamber.

Various features of the invention are set forth in the following claims.

What is claimed is:
 1. A probe for use within a living body, comprisingacatheter tube having a distal end; a three dimensional structure on thedistal end having an open interior area, the structure having anexterior surface for contacting tissue within the living body; asteerable support body carrying at least one ablating element andextending from the distal end of the catheter tube into the openinterior area of the structure, the steerable support body and the threedimensional structure both being integral with the catheter tube; and amechanism to steer the steerable support body within the open interiorarea.
 2. A probe according to claim 1, wherein the at least one ablatingelement emits electromagnetic microwave energy.
 3. A probe according toclaim 1, wherein the at least one ablating element includes an antenna.4. A probe according to claim 3, wherein the antenna forms a helix withabout 10 turns.
 5. A probe according to claim 3, wherein the operatingfrequency of the antenna is either approximately 915 MHZ orapproximately 2450 MHZ.
 6. A probe according to claim 3, wherein theantenna is enclosed within a shroud of potting compound.
 7. A probeaccording to claim 6, wherein the potting compound shroud comprises amaterial made of a high dielectric constant, low microwave energy loss,and high thermal conductivity.